1. Field of Invention
This invention relates to hemostasis valves. More particularly, this invention relates to a universal hemostasis valve which is useful with a variety of catheters having a wide range of diameters.
2. Prior Art
The introduction of catheters into blood vessels for a variety of purposes such as coronary angiography has been known for many years. Several techniques for introducing these catheters are available. One such technique is the cut-down method. Another is the Seldinger technique. This technique involves surgically opening a vein or artery with a needle, inserting a guidewire into the vein or artery through the lumen of the needle, withdrawing the needle, inserting over the guidewire a dilator located inside an associated hemostasis valve and sheath, removing the dilator and inserting a catheter through the hemostasis valve and sheath and into the blood vessel.
Various types of hemostasis valves have been known in the prior art. However, in most cases hemostasis valves are designed for use with a particular size of catheter. Because adequate sealing around the catheter walls cannot be obtained for a wide variety of catheters having a range of diameters, it has not been possible in the past to employ a single hemostasis valve with catheters of widely varying diameters.
This problem is particularly acute when the guidewire technique is used. Guidewires are of extremely small diameters-often less than 0.050 inch. However, many catheters are relatively much larger in diameter. Therefore, in the prior art it has been difficult to design a hemostasis valve which will seal around both relatively large diameter catheters as well as relatively small diameter guidewires.
Prior art hemostasis valves have, in many instances, been of the gasket sealing type such as, for example, those shown in U.S. Pat. No. 4,000,739 which employs two gaskets to seal against the back pressure of blood in the cannula unit. The first, donut-shaped, gasket is provided with a hole slightly smaller than the diameter of the catheter to be inserted, while the second gasket is provided with a Y-shaped slit. When guidewires or catheters which are too small in diameter are inserted into this hemostasis valve, the sealing advantages of the first, donut-shaped gasket are no longer available because the larger diameter "donut holes" will not seal around the smaller diameter guidewire or catheter. Moreover, when catheters are employed having diameters which are extremely large in relation to the diameter of the hole in the donut-shaped gasket, the gasket may become separated from the hemostasis valve body or it may be unduly stretched so that it will not seal properly when a smaller sized catheter is inserted at a later time.
Hemostasis valves having similar problems are also disclosed in U.S. Pat. Nos. 4,673,393 and 4,610,665.
U.S. Pat. No. 4,436,519 discloses a combination of a donut-shaped gasket and a second cup-shaped seal. Like the prior art, two gasket hemostasis valves described above, the device described in the '519 patent suffers the same deficiencies because its donut-shaped gasket can only accept catheters having a relatively limited range of diameters. Moreover, this device is particularly susceptible to leakage when only the guidewire is in place.
U.S. Pat. No. 4,655,752 discloses a surgical cannula which does not employ donut-shaped gaskets. However, this cannula, like the other prior art cannulas, suffers from a lack of universality and from poor sealing. While two seals are employed, the second seal may only be used with catheters having a limited range of diameters and will provide little or no sealing for a guidewire.
Another problem shown by many prior art hemostasis cannulas is that the surgeon must be able to "feel" the catheter as it is inserted through the gaskets or other sealing members of the hemostasis valve and ultimately into a blood vessel. If insertion of the catheter through the hemostasis valve is too difficult, the cannula unit may be rejected by surgeons as being difficult to use during catheter insertion. Concomitantly, the use of hemostasis valves which exert undue pressure on the side walls of inserted catheters may lead to excessive hemodynamic dampening of the catheter. In other words, excessive pressure on the exterior side-walls of a catheter may cause a narrowing of the catheters diameter thereby altering measurement parameters within the catheter.
Thus, it is important in providing a sealing mechanism for a hemostasis valve unit that the mechanism:
1. be universal, i.e., useful with both guidewires and with catheters having a wide range of diameters;
2. provide for relatively easy insertion of all diameters of catheters; and
3. be free from excessive restriction which would cause hemodynamic dampening.
German Patent No. 3,042,229 purports to describe a hemostasis valve which may be used with catheters having a variety of diameters. However, it is extremely difficult to use this valve when relatively large diameter catheters are employed because the second seal, as shown in the patent, is required to expand against the sidewalls of the cannula, thereby, significantly increasing friction during insertion and the risk of hemodynamic dampening. Moreover, the sealing means of the device described in the '229 patent is formed from two separate pieces thereby increasing the difficulties of manufacture and the likelihood that one of the seals may become dislodged particularly during use with large sized catheters.
Accordingly, it is an object of this invention to prepare a hemostasis valve unit.
Another object of this invention is to prepare a hemostasis valve which is universal in nature and may be used with a wide variety of both large and small diameter catheters, without leakage.
It is another object of this invention to prepare a hemostasis valve which will not leak when it is inserted into a vein or artery over a guidewire.
It is a further object of this invention to prepare a hemostasis valve having a unitary sealing member forming at least two separate sealing sections.
It is yet another object of this invention to construct a hemostasis cannula unit which will permit the use of catheters having a wide variety of diameters, while at the same time allowing insertion of any of these catheters without undue pressure/friction thereby providing good surgical "feel" for all diameters of catheters and reduced hemodynamic pressure dampening.
These and other objectives are obtained by constructing the hemostasis cannula units of the instant invention.